A secondary battery, which has high application easiness according to a product group and an electric characteristic, such as a high energy density, has been universally applied to an electric vehicle (EV), a hybrid vehicle (HV), and the like driven by an electric driving source, or an energy storage system (ESS), an uninterruptible power supply (UPS) system, or the like using a medium and large battery used for household or industry, as well as a portable device.
The secondary battery attracts attention as a new energy source that is environmentally-friendly and improves energy efficiency in that it is possible to innovatively decrease use of fossil fuel, which is the primary advantage, while not generating a by-product when using energy.
The battery applied to the EV or the energy storage source is generally used in a form, in which a plurality of unit secondary battery cells is combined, to improve adaptiveness to a high capacity environment, which, however, is not essentially applied to a case where the secondary battery is implemented as a battery of a portable terminal and the like.
In general, a power source used for charging the battery is a direct current, and a power source generated and produced through a motor and the like is an alternating current. Accordingly, in order to charge the battery, it is necessary to convert the alternating current power source, which is generated and produced, into the direct current power source, and a rectifier performs the conversion. That is, the battery receives a current required for charging through the rectifier.
In a case of a lead storage battery in the related art, which is used for a vehicle and the like before a lithium secondary battery, internal resistance of the lead storage battery is high and thus a current value of a current flowing into the battery during the charging is not large, so that there is no concern in view of problems incurred in a battery, and thus a current control function of limiting the current flowing into the battery is not required. Accordingly, the rectifier connected with the lead storage battery in the related art does not have the current control function.
In contrast to this, in a case of the recent lithium secondary battery used for an EV and the like, internal resistance of the lithium secondary battery is low and thus a current value of the current flowing into the battery during charging is large, so that a current control function of limiting the current value is required.
Accordingly, in a case where it is desire to replace the lead storage battery with the lithium secondary battery in a device using the existing lead storage battery, there is a problem in that it is impossible to easily replace the lead storage battery due to the non-existence of the current control function.
Further, in equipment, which uses a plurality of batteries by connecting the plurality of batteries in parallel due to a necessity of a high capacity and the like, it is difficult for the rectifier to control a current, such that it is necessary to separately perform the current control function in order to protect the battery.